1. Field of the Invention
The present invention relates to a dynamic speaker, and particularly to a structure for fixing a voice coil to a diaphragm in the dynamic speaker.
2. Description of the Related Art
As one type of a speaker, a dynamic speaker has been known heretofore. The dynamic speaker, as disclosed in, for example, JP-A-6-178390, comprises generally a diaphragm, a voice coil of which one end portion is fixed to the diaphragm, and a magnetic circuit unit defining a cylindrical magnetic gap for placing the other end portion of the voice coil therein.
As the fixing structure of the voice coil to the diaphragm, the following structure is known, as disclosed in the JP publication. One end portion 2a of a voice coil 2 having an I-shaped coiling section as shown in FIG. 5A is bonded and fixed to a diaphragm 4.
However, in the speaker having such a fixing structure, since the large bonding area cannot be obtained, the fixing strength is insufficient. Accordingly, there is fear that the voice coil 2 peels off and separates from the diaphragm 4 during being used. Particularly, in case that the speaker is mounted on an automobile or the like, since it is used under environment where considerable vibration and shock load are applied, the voice coil 2 is easier to separate from the diaphragm.
On the other hand, as shown in FIG. 5B, in case that the coiling thickness of the voice coil 2 is set large, the relatively large bonding area between its one end portion 2a and the diaphragm 4 can be obtained, whereby the sufficient fixing strength can be obtained.
However, in this case, since a width of a cylindrical magnetic gap G of a magnetic circuit unit 6 becomes large, there is a problem that electroacoustic conversion efficiency of the speaker degrades. Further, the larger the coiling thickness of the voice coil 2 is, the larger the weight of the voice coil 2 becomes, whereby the large load acts on the bonding surface. Therefore, there is also a problem that separation preventing effect cannot be obtained as expected.
The invention has been made in consideration of these circumstances, and an object of the invention is to provide a speaker in which separation of a voice coil can be prevented without worsening acoustic characteristic of a dynamic speaker.
In order to achieve the object, a coiling sectional shape of the voice coil has been improved by the invention.
Namely, there is provided a speaker comprising:
a diaphragm;
a magnetic circuit unit defining a cylindrical magnetic gap; and
a voice coil having a first portion bonded to the diaphragm, and a second portion placed in the cylindrical magnetic gap;
wherein a thickness of the first portion of the voice coil is set larger than that of the second portion of the voice coil.
The xe2x80x9cdiaphragmxe2x80x9d and xe2x80x9cmagnetic circuit unitxe2x80x9d are not particularly limited in their concrete constitution such as their material, shapes, and the like as long as they can be used as a component of the dynamic speaker.
Further, the xe2x80x9cvoice coilxe2x80x9d is not particularly limited in its concrete coiling sectional shape as long as its coiling thickness at the first portion is set larger than that at other portions.
As indicated in the constitution, in the speaker according to the invention, the first portion of the voice coil is bonded and fixed to the diaphragm. Since the coiling thickness of the voice coil at the first portion is set larger than that at the other portions, the large bonding area between the first portion thereof and the diaphragm can be obtained without considerably increasing the weight of the voice coil. Therefore, it is possible to prevent the large load onto the bonding surface caused by the increase of the weight of the voice coil unlike the case where the coiling thickness of the voice coil is made large in whole, and the sufficient fixing strength of the voice coil in relation to the diaphragm can be obtained.
Further, since the coiling thickness of the voice coil at the other portions is set relatively small, it is not necessary to expand the width of the cylindrical magnetic gap in the magnetic circuit unit, and the large bonding area can be obtained between the first portion thereof and the diaphragm. Therefore, without lowering electroacoustic conversion efficiency of the speaker, the effects can be obtained.
As described above, according to the invention, the separation of the voice coil can be prevented without worsening properties of the speaker in the dynamic speaker.
In the constitution, as described above, the coiling sectional shape of the voce coil is not limited particularly. In case that the coiling section is substantially L-shaped by forming a flange that protrudes inward in the radial direction at the first portion, the large bonding area can obtained in a state where the increase of the weight of the voice coil is kept to a minimum. Further, without considerably complicating the coiling operation of the voice coil, the coiling thickness of the voice coil at the first portion thereof can be set larger than that at other portions.